JPS6188549A - Semiconductor integrated circuit with detecting circuit for life of battery - Google Patents

Abstract

PURPOSE:To obtain a battery-life detecting circuit having no temperature dependence by using the series connection of a diffusion resistor and a MOS resistor, temperature coefficient thereof are approximately equal, as the constituent of the detecting circuit in an IC incorporating the detecting circuit. CONSTITUTION:A battery-life detecting circuit incorporated into an electronic clock IC, etc. is constituted by a series resistor consisting of a diffusion resistor 11 and a MOS resistor 12 having approximately equal temperature coefficients. The surface impurity-concentration of the diffusion resistor 11 is brought to 1X10<18>/cm<3> or more and diffusion depth thereof to 1mum or less at that time, and the temperature coefficient thereof is conformed approximately to that of the MOS resistor 12. The IC has C-MOS constitution composed of a P channel MOS transistor 13 and an N channel MOS transistor 14 connected between potential VDD and VSS, and the diffusion resistor 11 and the MOS resistor 12, which are connected in series and have no temperature dependence, are fitted in parallel with the IC. The IC is constituted in this manner and each middle point is connected, a sampling signal is inputted to the resistor 12, and a sensing signal is outputted from the middle point of the C-MOS.

Description

[Detailed description of the invention] [Field of application on Lψ, 4] The present invention is a battery life detection circuit (hereinafter abbreviated as BIJu path).
Regarding semiconductor integrated circuit (hereinafter abbreviated as IC) K with built-in
In particular, it relates to improving the temperature characteristics of the BD circuit.

[Conventional technology]

In the BD circuit built into electronic clock IC, etc.
A system is known in which a decrease in battery voltage is detected using a series connection of a ~103 resistor and a '4 voltage-independent resistor. An example of such a BD circuit is shown in FIG. In Figure 82, 11 is a resistor with no voltage dependence, and 12 is 1 lil.
US resistor, 16 is a p-channel to 1S transistor, and 14 is an n-channel MOS transistor. 16 and 14 are complementary M (JS configurations, when the input level is higher than a certain boundary value, the sense signal output is Low, and when the input level is LO to V from the boundary value, the sense signal output is is Hi
It becomes gh.

~10S resistance σ- Since the resistance value increases as the voltage decreases, in Figure 2, when the battery voltage is normal, 11 and 1
1 so that the partial pressure due to 2 is determined as the input of 16 and 14 to be slightly τLu~V than the boundary value.
By setting the resistance values of 1 and 12, the sense output signals of 16 and 14 can be inverted when the battery voltage decreases. This is the operating principle of battery life detection in the BD circuit shown in FIG.

Current flows through 11 and 12 only when l-1-1i is input as a sampling signal, but 1
If the resistance values of 1 and 12 are low, the current will be large, and the power consumed by the BD circuit will be large.

Therefore, the resistances 11 and 12 are usually set to several hundreds of ohms. In order to realize a resistance that bends within a practically allowable range, the sheet resistance of the resistor 11 must be 077 or more for 1 to 2. Therefore, in the past, the 11 resistors were realized with P-well resistors or polysilicon resistors.

[Problem that the invention seeks to solve]

However, at the so-called normal temperature of -20 to +80℃, the temperature coefficient of M (JS resistance is 02 to 03%/
'deg, whereas the P-well resistance is about 07%/(
leg, and the polysilicon resistance is -6 to -01%/d
eg, so these are 1. '4 The completed BD circuit is
There were five problems when the mixed pond longevity product detection i1j pressure changed depending on the temperature.

Therefore, an object of the present invention is to provide a 131) circuit without temperature dependence.

[Means for solving problems]

The first feature of the present invention is that a diffused resistor having a temperature coefficient approximately equal to that of the MO3 resistor is used as the 11 resistors in the 21 y and 21 l. It is clear that if the temperature coefficients of 11 and 12 are equal, the BD circuit σ) has no temperature dependence. The reason why a diffused resistor is used as the resistor 11 is that among the IC components, it is easiest to realize a temperature coefficient of 02 to 03%/deg.

The second feature of the present invention is that the surface impurity concentration of the diffused resistor is set to 1Xl018c+n~3 or more. The reason is as follows.

At normal temperatures, the donor and acceptor are completely ionized, and there is no change in the number of carriers. Therefore, a concentration change in diffused resistance is a temperature change in mobility. Move
If the conditions such as crystal defects are the same, the h degree is determined by the scattering of carriers by the ions of ionized donors and acceptors, and by the field.
It is determined by carrier scattering due to lattice vibration. Among these, the scattering cross section due to lattice vibration directly depends on the magnitude of the lattice vibration, and therefore has extremely high temperature dependence. On the other hand, since the electric field caused by impurities spreads over a very wide range, the scattering cross section is very large, and the increase in the scattering cross section due to lattice vibration can be ignored. In other words, carrier scattering due to impurities does not depend on temperature.

Therefore, the higher the impurity concentration of the diffused resistance, the smaller the temperature change during movement. At an impurity concentration of -3 of I x 10'8, the temperature coefficient of mobility is approximately -0.5%/d
It is eg. Therefore, the temperature coefficient of such a diffusion resistance of Ir) degrees is approximately +05%/deg''C-.

Temperature coefficient of 405 resistance is 0.2-0.3%/d
eg, in order to make the temperature coefficient of the diffusion resistance equal to or close to this value, the surface concentration of impurities must be at least l x 101'cra-3 or more.

This is the reason for the second feature.

The third feature of the present invention is that the diffusion depth of the 11 diffused resistors in FIG. 2 is set to 1 ttm or less. The reason is as follows.

As mentioned above, the sheet resistance of resistor 11 is Ω1 for 1 to 2.
I have no choice but to make it more than one. The surface concentration of impurities is l
] 018crn-”, the diffusion depth is I, Ir
The note resistance of the diffused resistor of 2 is 1 to 2 Ω,/co.

Therefore, an expansion 1:j with a surface concentration of I x 10'6 儂-3 or more and a note resistance of 1 to 2 Ω/min or more
In order to achieve l resistance, the diffusion depth must be less than 1 μm. This is the third hidden feature.

〔Example〕

Embodiment 1FII of the present invention will be described below with reference to the drawings.

FIG. 1 shows a diffused resistor according to the invention and an n-channel λIO
This is a graph showing the ratio of the temperature change rate with 5 resistors, and 2
It shows how many °C the resistance value increases or decreases at each temperature with respect to the resistance value at 0 °C. In Fig. 1, 21 and 22 are respectively expanded (1 is resistance').

3\Is Temperature change of the abrasive resistor; (, -. Diffusion resistance is 10"' Cm3 (C
In the form of diffused resistance, the surface degree: i approx. 3 X l O" c
m” and the diffusion depth is approximately 0.25 tlm.

As is clear from FIG. 2, if the present invention is put into practice, it is possible to obtain an expanded resistor with a temperature coefficient of Sl (approximately equal to the JS resistance).

Figure 213 shows '11 when the present invention is applied to the D circuit.
℃ Also shows the temperature characteristics of the life detection voltage. The detection voltage is almost constant within the normal temperature range, within ±6 mV.

[Effect of Aming]

As is clear from the above explanation, according to the present invention, B I)
It becomes possible to eliminate the temperature dependence of the circuit, and if it is applied to ICs for slave clocks, the effect will be enormous.

[Brief explanation of drawings]

Fig. 1 is a graph of the temperature change rate of the diffused resistance and klOS resistance of the present invention, and Fig. 2 is a BD graph explaining the conventional and the present invention.
The circuit diagram of the circuit, FIG. 3, is a graph showing the temperature characteristics of the battery life detection voltage of the BD recycling according to the present invention. 11...Temperature-dependent (resistance), 12...N40S resistance, 16...p-channel MOS transistor, 14...
...n-channel N103) transistor, 21...temperature change rate of diffused resistance according to the invention, 22...temperature change rate of 105 resistance to 0 channel. Patent Applicant Nchizun Watch Co., Ltd. Figure 1 H degree (0C) 21 'I am a 94th generation old man.
n child ff J channel MOS dirt j le's eyebrows L change I am sorry Figure 2 n and degree (°C)

Claims (3)

[Claims] (1) A semiconductor integrated circuit incorporating a battery life detection circuit, characterized in that the battery life detection circuit has, as a component of the battery life detection circuit, a series connection of a diffused resistor and a MOS resistor having substantially equal temperature coefficients. Semiconductor integrated circuit with. (2) The diffused resistance whose temperature coefficient is almost equal to the MOS resistance is
The semiconductor integrated circuit with a battery life detection circuit according to claim 1, wherein the surface impurity concentration is 1×10^1^8 cm^-^3 or more. (3) The diffused resistance whose temperature coefficient is almost equal to the MOS resistance is
A semiconductor integrated circuit with a battery life detection circuit according to claim 1, wherein the diffusion depth is 1 μm or less.